A Simple Computational Model for Acceptance/Rejection of Binary Sequence Generators

A simple binary model to compute the degree of balancedness in the output sequence of LFSR-combinational generators has been developed. The computational method is based exclusively on the handling of binary strings by means of logic operations. The proposed model can serve as a deterministic alternative to existing probabilistic methods for checking balancedness in binary sequence generators. The procedure here described can be devised as a first selective criterium for acceptance/rejection of this type of generators.Comment: 16 pages, 0 figure

Icosahedral Ni nanowires formed from nanocontacts breaking: Identification and characterization by Molecular Dynamics

We present and discuss an algorithm to identify and characterize the long icosahedral structures (staggered pentagonal nanowires with 1-5-1-5 atomic structure) that appear in Molecular Dynamics simulations of metallic nanowires of different species subjected to stretching. The use of this algorithm allows the identification of pentagonal rings forming the icosahedral structure as well as the determination of its number np , and the maximum length of the pentagonal nanowire Lpm. The algorithm is tested with some ideal structures to show its ability to discriminate between pentagonal rings and other ring structures. We applied the algorithm to Ni nanowires with temperatures ranging between 4K and 865K, stretched along the [111], [100] and [110] directions. We studied statistically the formation of pentagonal nanowires obtaining the distributions of length Lpm and number of rings np as function of the temperature. The Lpm distribution presents a peaked shape, with peaks located at fixed distances whose separation corresponds to the distance between two consecutive pentagonal rings

Decrease of the adhesion force with vapor pressure

Trabajo presentado a NanoSpain 2010 celebrado en Málaga del 23-26 Marzo, 2010. -- Incluye comunicación oral y póster.Experimental evidence of a monotonous decrease of the capillary forces between hydrophilic surfaces with increasing relative humidity from 0 to 100% is presented. In concordance with the results of a theoretical simulation, we identified the objects’ shape as the origin of different adhesion force vs. RH behaviours when treating with nanoscale objects. If the water neck is formed between a flat surface and a nanometric object presenting a truncated cone shape the adhesion force decreases with increasing vapour pressure. The variety of meniscus force behaviours found for different shapes emphasizes the importance of geometry in capillary phenomena at the nanometric scale.Peer reviewe

Estudio estadístico del transporte electrónico en sistemas de baja dimensionalidad

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia Condensada. Fecha de lectura: 26-11-199

On the optimal conditions for the formation and observation of long icosahedral nanowires of aluminium, nickel and copper

This article presents a statistical study based on molecular dynamics simulations of the formation of icosahedral nanowires from the breakage of Al, Ni and Cu nanowires. These icosahedral nanowires, which show large stability, are created by the emergence of new units of 5 + 1 atoms (atomic pentagonal rings plus one atom at the top) due to the anisotropic growing mechanism induced by nanowire stretching. The appearance of each new 5 + 1 atomic set (an inelastic atomic rearrangement) during the stretching is matched with a sudden decrease of the force exerted on nanowire extremes. We have also demonstrated that the icosahedral formation is favoured when stretching takes place along the [1 0 0] and [1 1 0] crystallographic directions. We demonstrate that, as result of a balance between two competitive mechanisms, there exists an optimal temperature that provides the larger icosahedral nanowires production for each metallic species. © 2013 IOP Publishing Ltd.This work has been partially supported by the Spanish MICINN through projects FIS2009-13430-C01/C02, FIS2012-36113-C01/C02 and CSD2010-00024 (Forces for Future) and by the Madrid Regional Government through the Programs CM-S2009/MAT1467 (NanoObjetos-CM) and CM-S2009/TIC-1476 (Microseres-CM).Peer Reviewe

Design of Balanced Binary Sequences for Cryptographic Applications

5 pages, 2 tables.-- Communication presented at the 5th World Multiconference on Systemics, Cybernetics and Informatics and 7th International Conference on Information System Analysis and Synthesis (SCI/ISAS 2001, Orlando, Florida, Jul 22-25, 2001).An easy method of computing the number of 1's in the binary sequences obtained from either non-linear filter generators or combination generators is developed. The procedure is based exclusively on the handling of binary strings by means of logic operatots (OR, AND) and can be applied to nonlinear generators in a range of cryptographic interest. As a straight consequence of this method, simple rules to design generators producing balanced (quasi-balanced) systems are also derived.Peer reviewe

Diffractive magneto-optics, magnetic interactions, and reversal mechanisms in Co microsquare arrays

The magneto-optical properties of Co microsquare— 2 μm edge—arrays have been investigated for different interelement separations, from 0.2 to 2.0 μm . The magneto-optical response is measured both at reflected and diffracted beams, and it is compared with the results of a model that uses micromagnetic simulations and optical diffraction theory to calculate the magneto-optical response for different diffracted spots. A satisfactory agreement between the experiments and the predictions from the combined micromagnetic and optical diffraction models allows the interpretation of the experimental data and provides a way to analyze and understand the physical meaning of the magneto-optic diffracted signal. The comparison of this diffracted magneto-optical experimental data with predictions from simple reversal models allows us to monitor different element magnetization reversal mechanisms as the separation between elements in the array varies.R.A.S. acknowledges support from the “Consejería de Educación de la Comunidad de Madrid.” Research funded through EC-G5RD-CT-2002–00731 HIDEMAR project.Peer reviewe

Negative dissipation gradients in hysteretic materials

Measuring energy dissipation on the nanoscale is of great interest not only for nanomechanics but also to understand important energy transformation and loss mechanisms that determine the efficiency of energy of data storage devices. Fully understanding the magnetic dynamics and dissipation processes in nanomagnets is of major relevance for a number of basic and applied issues from magnetic recording to spin-based sensor devices to biomedical magnetic-based hyperthermia treatments. Here we present experimental evidence for a counter-intuitive monotonical reduction of energy dissipation as the interaction between two nanomagnets is enhanced. This behavior, which takes place when spins are parallel, can be understood in terms of hysteresis phenomena involved in the reorientation of these spins. The measured magnetic losses of about a few femtowatts are in agreement with quasi-static micromagnetic numerical simulations.We gratefully acknowledge funding from projects CSD2010-00024 and MAT2013-48059 (MINECO)